This invention relates to the removal of tissue from the body such as for example removal of cataracts from the eye.
It is known to remove diseased tissue from the body by fragmenting, crushing or otherwise making the tissue flowable while in the body and then aspirating it. In one known class of surgical techniques of this type specifically intended for the removal of cataracts: (1) an incision is made along the superior corneal margin from about 10 to 2 o""clock (12 o""clock is the location closest to the top of the head of the patient) approximately 10 mm in chord length; (2) an incision is made in the capsular wall; and (3) the cataract is removed. The anterior chamber is maintained substantially formed during the operation by means of a continuous inflow of irrigating solution.
In one prior art technique of this class for removing a cataract, the nucleus is expressed out of the eye and the cortex is removed by a process of irrigation and aspiration. In another prior art technique of this class for removing the cataract, the nucleus is removed with a vectis and about 0.1 milliliter of viscoelastic compound or irrigating fluid is introduced into the capsular bag to separate the capsular walls. With the capsular walls separated, a wedge of the cortex is engaged in the aspiration port of a cannula and peeled toward the center and then aspirated to remove it. This process is repeated so that the layers of the cortex are peeled and then aspirated inwardly through the cannula, layer by layer, until the intact capsular bag (except for the horizontal incision) is completely empty and clean.
This technique of removing the cataract is disclosed by Anis, Aziz Y., xe2x80x9cIllustrated Step-by-Step Description of the Anis Dry Extra Capsular Cataract Extraction Technique With In-the-Bag Lens Implementationxe2x80x9d; Seminars in Opthalmology v. 1, N. 2 (June), 1986, pp. 113-129 and the technique is compared with other such techniques of this class.
Two prior art types of instruments which aid in the fragmentation and aspiration of the lens nucleus to permit extraction through a small incision are disclosed in U.S. Pat. No. 3,589,363 to Anton Banko et al.; U.S. Pat. No. 3,902,495 to Steven N. Weiss; U.S. Pat. No. 3,693,613 to Charles Kelman et al.; and U.S. Pat. No. 4,041,947 to Steven N. Weiss et al. This instrument is intended in the prior art to fragment a lens nucleus using ultrasonic vibrations to aid the irrigation/aspiration of the lens. The ultrasonic vibrations laterally reciprocate the tip of an instrument to fracture the cataract after which it can be aspirated.
A further type of instrument is disclosed in U.S. Pat. No. 4,908,015 issued to Anis on Mar. 13, 1990. This patent describes an instrument which rotates a solid member having blades extending from it to grind the lens.
These tissue removal techniques have several disadvantages, such as: (1) they risk tearing the capsular wall with the reciprocating ultrasonic vibration tools or with the rotating blades; (2) under some circumstances, they require large incisions in or removal of parts of the capsular wall; and (3) they may require the use of several different instruments.
Still another type of prior art technique for removing cataracts is disclosed in U.S. Pat. 3,996,935 to Banko issued Dec. 14, 1976. This type of instrument shows cooperating jaw-like members, one of which rotates inside the other to break up the lens by shearing sections of it. It aspirates fragments through the instrument. This type of instrument has a disadvantage in that it can break the capsular wall and is relatively complex. Part of the disadvantage comes from the teaching that it may be rotated manually or mechanically without a corresponding teaching of the rate of rotation required for efficient use.
Still another prior art instrument includes a small rotary magnetic cutter that is injected through the capsular wall and a means for applying magnetic fields that control the magnetic cutter in position. The small magnetic cutter is rotated as it moves from position to position in the capsular bag and to abrade or cut the lens that is to be removed.
This instrument has several disadvantages, such as: (1) it is relatively complicated and expensive because of the need to remotely control the small cutter; and (2) it does not incorporate any mechanism for aspirating the lens particles as they are abraded from the lens.
In still another prior art device disclosed in U.S. Pat. No. 4,002,169, small retractable wires are rotated in a range of 5 rpm to 16,000 rpm. There is no teaching of selecting the speed for surface discrimination and the device relies on blunt surfaces to avoid damage to the capsular wall instead. This device has the disadvantages of: (1) providing a relatively slow cutting velocity range with blades not shaped for cavitation or turbulance; (2) not providing a range of velocities sufficient to form small particles that can be aspirated through a small hole; and (3) not providing for aspiration during fragmenting, thus blocking visibility with particles.
Each of these prior art types of instruments includes a handpiece and a console. The handpiece is held by the surgeon and includes an operative tip that, at one point in time, enters the capsular sac to fragment and remove the cataract. The console includes controls for the handpiece such as those that control the direction of movement and speed of movement of the tip, rate of flow of liquids, the suction or aspiration pressure and the drivers that apply power to the hand-piece at the appropriate values. Generally, the consoles are designed together with a particular type of hand-piece used in a specialized technique of ocular surgery.
A still further type of instrument is disclosed in U.S. Pat. No. 4,504,264 to Kelman issued Mar. 12, 1985. This patent discloses an instrument that reciprocates a cutting tip ultrasonically and oscillates it rotationally about its longitudinal axis at a rate of one hertz through an angle of between five degrees to 60 degrees. Because of dwell time at each change of rotational direction and speed limitations inherent in the direction changes, this instrument does not provide the advantage of breaking the tissue into particles so small as to not cause plugging nor impede visibility of the instrument tip.
The prior art arrangement has several disadvantages, such as for example: (1) it is difficult for the surgeon to use the most modern techniques without investing substantial amounts of money in purchasing additional consoles for the newer instruments; (2) for each new handpiece designed for a particular technique, the surgeon must adapt to different controls in the console itself rather than relying upon controls with which he is already familiar; (3) the handpieces are subject to causing plugging, poor visibility into the eye and excessive pressure on the capsular wall from movement of large particles; and (4) different equipment is necessary to remove vitreous liquids.
Accordingly, it is an object of the invention to provide a novel technique for tissue removal.
It is a further object of the invention to provide a novel instrument for fragmenting and removing a cataract during cataract removal surgery with low risk of damage to the capsular wall.
It is a still further object of the invention to provide a novel instrument designed to fragment tissue without damage to the nearby tissue such as for example not damaging the capsular wall while removing the lens during cataract removal surgery or not damaging artery or vein walls while removing cancerous tissue near the vein or artery.
It is a still further object of the invention to provide a novel instrument and method for removing tissue that powders the tissue and aspirates it while maintaining good visibility.
It is a still further object of the invention to provide a novel interface that permits the connection of a phacotmesis handpiece to consoles designed specifically for other ocular surgery such as consoles designed originally to cooperate with a phacoemulsification handpiece.
It is a still further object of the invention to provide an instrument capable of vitrectomy and removal of cateracts with the same handpiece.
In accordance with the above and further objects of the invention, an incision is made for the insertion of a surface-discriminating, fragmenting tool. The surface-discriminating, fragmenting tool fragments and permits aspiration of high mass, rough-surface, rigid tissue without damaging nearby smooth, flexible, low mass walls. The tool fragments some tissue but avoids fragmenting other tissue by discriminating between tissues. This discrimination is based on one or more of several factors including: (1) the rigidity of the tissue; (2) the amount of mass of the tissue; (3) the angle of the tissue to the direction of movement of the tool; (4) the roughness of the surface of the tissue; and (5) the size and shape of the surface of the tissue to the extent the size and shape affect the tendency of the negative pressure created by aspiration and/or irrigation to move the tissue toward the surface-discriminating, fragmenting tool.
The surface discrimination of the tool is controlled by moving surfaces which fragment diseased tissue on impact, referred to as phacotmesis, and cause cavitation forces that further fragment and mix fragments of tissue, referred to as phacocoelosis, but which move at a rate of speed slow enough so that the more integrated, more flexible, lower mass and smoother tissue is moved away without fragmenting. The tissue is not constrained by opposed shear forces of the tool as in some prior art rotating tools nor is the higher mass, rigid tissue moved significantly as a bulk.
The surfaces of the instrument fragment tissue that: (1) is stiffer and has a higher modulus of rigidity; and (2) is at an angle to the cutting edge closer to 90 degrees and receives less force moving it away. Thus, the surgeon removing a cataract adjusts the speed of movement of the tool surfaces, the aspirating and irrigation forces, the rake angle of the tip and the cavitation level as controlled by the position of the tool surface, the velocity and the shape of the moving surface. The adjustment is made to fragment the cortex because of its higher mass, modulus of elasticity and projections in the path of the tool surfaces but to move the capsular wall because of its lower mass, lower modulus and fewer projections closer to 90 degrees and not fragment it.
In one embodiment, a moving, fragmenting surface moves at an angle with the normal to a cataract surface, which angle is obtuse and generally close to being perpendicular to the normal in such a manner as to mix particles and to cause or aid ultrasonic motion normal to the tissue in causing cavitation and in fragmenting and mixing the cataract particles while maintaining the direct force on the cataract that could accelerate tissue against the capsular wall relatively low. In a preferred embodiment, the fragmenting surface is moved ultrasonically along the normal while it is moving at an angle to the normal such as by rotating continuously at least through several 360 degree rotations in one direction.
The aspiration pressure is more effective within the moving surfaces of the rotating tip. It is low enough to pull the fragmented tissue and tissue to be fragmented but it does not hold the smooth flexible capsular wall against movement away from the moving surfaces of the tool. The rotating surfaces move the smooth wall outwardly and provide some counter pressure to the aspirating pressure inside the fragmenting zone. The vibrating speed and rotational speed can be adjusted to powder the cataract so as to maintain good visibility and ease of aspiration and can be adjusted for vitrectomy.
In the case of cataract removal surgery, a small incision of two to seven millimeters and preferably three millimeters is made in the sclera along the corneal border at 12 o""clock and another incision of similar dimension or a round hole is made in the anterior capsular wall. The instrument is inserted and fragments the lens matter without fragmenting the capsular wall. The factors useful in surface-discriminatory, fragmenting differ from eye to eye or tissue to tissue and may be selected in accordance with the surgeon""s observations. These factors are the speed of the moving surfaces with respect to the tissue, the holding pressure from aspirating vacuum and irrigating liquid, the location and position of the moving surfaces, the rake angle of the cutting edge of the moving surfaces and the shape of the portions of the moving surfaces most related to cavitation. These factors are established by the surgeon as a function of the mass of the capsular wall and the mass of the tissue to be fragmented, the stiffness and smoothness of the capsular wall or other healthy smooth tissue and the hardness and flexibility of the tissue.
In one embodiment, moving surfaces of the fragmenting tool hit the cells at a substantially tangential angle and distort them or cut them with their leading edges while the trailing edges create cavitation that further breaks and mixes the tissue without imparting such force to the tissue in a direction that may injure the capsular wall. For large and rigid or for rough surfaces, the shear force and cavitation is sufficient for fragmentation whereas for more flexible, lower mass and smoother surfaces, the leading edges and the cavitation tend to move the surface away and thus avoid fragmentation. The aspirating port or ports tend to pull the fragmented material into the interior of the tool.
In a preferred embodiment, a tubular member has a central, aspirating channel along its longitudinal axis with one end having a fragmenting tip and the other end being adapted to rotate the tube. In one embodiment, the cavitation is at low frequency below the ultrasonic frequency range. In a preferred embodiment, the tip is rotated continuously in one direction for more than one 360 degree cycle and at the same time ultrasonically reciprocated.
As can be understood from the above description, the technique and instrument of this invention have several advantages, such as: (1) they selectively fragment some tissue without damaging other nearby tissue; (2) they are able to fragment, mix and aspirate tissue, and in the case of cataract removal, while maintaining good visibility; and (3) the same handpiece can perform vitrectomy.